Some communication networks, such as those used in data centers, route communications between devices using a network of switches. In some networks, the switches are Mach-Zehnder optical switches that use phase modulators and couplers, adjust the phase modulators' state to select which switch input and output ports are connected, and route light carrying signals to end devices (e.g., client device, a server). A Mach-Zehnder optical switch can split incoming light into components routed down multiple paths. The Mach-Zehnder optical switch then uses one or more phase modulators to create constructive or deconstructive interference in an output coupler at the potential output paths in order to select where the light is routed. Crosstalk between different light beams traversing the network of switches can arise due to the physical characteristics of the couplers and phase modulators, and can increase as light passes through successive switching nodes. Further, current approaches for reducing crosstalk, e.g., low-attenuation thermal switches, are power-hungry and cannot be implemented in network architectures that have a large number of switches, such as a modern optical switch network.